For electrical appliances that are supplied with an electrical AC voltage by means of forward phase control, the synchronization signal is a digital map of the AC voltage signal, and is therefore an important signal because it prescribes a clock for generating and processing further signals of the electrical appliances.
It is already known that electronics for such appliances can be put into a safe state when the electrical supply voltage is too low. For this purpose, it is possible to use what is known as a brownout module, for example, which is integrated in some microcontrollers. A disadvantage is that said modules are usually not freely configurable, however, which means that a threshold voltage to be monitored usually cannot be adjusted, can be adjusted only very coarsely or can be adjusted on the basis of the power supply using said modules. They normally switch the microcontroller to a reset state, as a result of which the microcontroller is then no longer able to react in a useful manner.
A circuit that triggers a reset for the microcontroller at the master clear connection is also known. Said circuit is implemented externally and therefore means space requirement and cost.
An internal module for a microcontroller is also known that implements monitoring from an electrical supply voltage for the microcontroller. By way of example, such a module is described in application note AN1072 “Measuring VDD Using the 0.6 V Reference” from Microchip Technology Inc.